How do I create a hinged wing?
For Tails consider a Armature a Spline Constraint, employing curves, which can provide the smooth visuals.  That is just a starter.
Armatures are suggested for Wings.  Thus you have control over the flapping motion. I assume you will need that control.  
You stated [I can't seem to remember how ..].  Consider a video website for tutorials. You may want to search .. Blender Tutorial Spline Constraint.
Once some of the basics are there you can consider hundreds of subtleties.